Problem: Solve the equation. $ 25 = 7 + r$ $r=$
Explanation: Subtract $7$ from both sides: 25 − 7 25 − 7 = = r 7 + r − 7 \begin{eqnarray} \\ \hphantom{25 {- 7}} &\hphantom{=}& \hphantom{r} \\ 25 &=& 7 + r \\ \\ {-7} && {-7} \\ \end{eqnarray} 25 − 7 = r \begin{eqnarray} \\ 25 {- 7} &=& r \\ \end{eqnarray} Simplifying, we get: $ r = 18$